A walking-beam conveyor has a plurality of rails or beams that extend horizontally next to one another. At least one of the rails is fixed and at least one is vertically and horizontally movable. The movable rails describe a quadrilateral motion cycle of up, forward, down, and back so as to lift objects off the stationary rails, advance them one step, drop them back on the stationary rails, and return with the objects sitting on the stationary rails.
French patent No. 2,531,044 describes such a conveyor used for moving bottles. It has rails whose carrying surfaces are each made of a succession of identical stainless-steel tubes that are fitted to mounts themselves fixed on the respective rail. Such a system is quite light, and the stainless-steel tubes are extremely resistant to corrosion.
Nonetheless such a system, in particular when used with glass objects which create very sharp and abrasive particles when broken, is subjected to substantial mechanical wear so that periodically some tubes have to be replaced. To replace about ten tubes in the middle of a beam 10 m long it is often necessary to take out several hundred tubes between the worn tubes and the closer end of the beam. This is a cumbersome job and one that is particularly irksome when an accident or the like has only damaged one of the tubes.